Low Nmp Aqueous Polyurethane Composition with Reactive Diluent

ABSTRACT

An aqueous composition comprising a polyurethane dispersion with a sediment content ≦5%, wherein the polyurethane has an acid value in the range of from 25 to 65 mgKOH/g and comprises (i) 36 to 60 wt % of at least one aromatic polyisocyanate and where the polyurethane is prepared in the presence of (a) ≦5 wt % of 1-methyl-2-pyrrolidinone by weight of the polyurethane and (b) at least one reactive diluent.

The present invention relates to an aqueous composition comprising apolyurethane dispersion, an aqueous composition comprising apolyurethane vinyl hybrid dispersion, a process for making the aqueouscompositions and the use of such aqueous compositions in coatings suchas coatings for floors.

It is well known in the coatings industry that polyurethane dispersionscan be applied to a variety of substrates to provide coatings with goodresistance to abrasion, good chemical resistance, good flexibility anddurability as well as having good adhesion to the substrate. A majorapplication for such coatings is as clear coatings for wood flooring.

Conventionally polyurethane compositions are prepared in organicsolvents which evaporate on drying after application to a substrate. Forreasons of environmental protection and adherence to solvent emissionguidelines water-based polyurethane dispersions and polyurethane vinylhybrid dispersions have been developed and are well known.

It is also known that polyurethanes based predominantly on aromaticpolyisocyanates have better hardness, better resistance againstchemicals and better mechanical properties in for example flooringapplications than polyurethanes based predominantly on aliphaticisocyanates. Furthermore the use of aromatic polyisocyanates tends to bemore cost effective than the use of aliphatic polyisocyanates.

U.S. Pat. No. 4,801,644 and U.S. Pat. No. 4,927,876 disclose thepreparation of aqueous polyurethane compositions containingdiphenylmethane-2,4-diisocyanate utilising 1-methyl-2-pyrrolidinone asan organic solvent.

U.S. Pat. No. 5,173,526 discloses a method for making aqueouspolyurethane-vinyl polymer dispersions with 1-methyl-2-pyrrolidinonebeing used as a solvent.

U.S. Pat. No. 5,314,942 discloses an aqueous polymer dispersioncontaining a vinyl polymer prepared in-situ and a water-dispersiblepolyurethane having pendent polyethylene oxide chains and utilising1-methyl-2-pyrrolidinone.

U.S. Pat. No. 6,239,209 discloses an air-curable polyurethane-acrylichybrid interpenetrating polymer network.

U.S. Pat. No. 6,566,438 discloses aliphatic polyurethane vinyl hybridcompositions containing 1-methyl-2-pyrrolidinone.

JP 06-08553 and JP 03-193446 disclose the preparation ofpolyurethane-polyurea dispersions.

However such water-based polyurethanes and polyurethane vinyl hybrids,especially if based on aromatic polyisocyanates, still utilisesignificant amounts of high-boiling and water-soluble solvents such as1-methyl-2-pyrrolidinone (NMP) to reduce the viscosity during productionand these solvents remain in the aqueous composition after dispersion ofthe polyurethane in water and then evaporate on drying.

Proposed changes in legislation on the labelling of products containingNMP are resulting in increased efforts to minimise and even eliminatethe use of NMP altogether.

U.S. Pat. No. 4,318,833 discloses water-reducible acrylic-urethanecoating compositions where the polyurethanes are prepared in a solventmixture.

U.S. Pat. No. 4,644,030 discloses aqueous polyurethane-polyolefincompositions.

U.S. Pat. No. 5,137,961 discloses the preparation of a surfactant freeaqueous polymer dispersion containing an anionic polyurethane basedsubstantially on aliphatic isocyanates and a vinyl polymer where vinylmonomers are used to reduce the viscosity of the reaction mixture.

U.S. Pat. No. 6,635,706 discloses a pre-crosslinked urethane-acrylicdispersion.

U.S. Pat. No. 6,635,723 discloses a process for making a solvent-freepolyurethane dispersion using a relatively low aliphatic polyisocyanatecontent.

U.S. Pat. No. 6,720,385 discloses aqueous polyurethane latexes preparedwithout the use of organic solvents using relatively high levels ofpolyethylene oxide polyols.

JP 09-150568, JP 09-150569, JP 09-102861 and JP 09-038674 disclose thepreparation of aqueous polyurethane compositions utilising unsaturatedmonomers and hydroxyl groups bearing organic solvents.

A disadvantage resulting from the preparation of polyurethanes based onaromatic isocyanates and with very low NMP levels or with no NMP at allis that the processing usually results in a high level of sedimentand/or gel. Furthermore in the prior art there is a desire to keep thelevel of polyisocyanate used in the polyurethane preparation to aminimum in order to get acceptable processing.

Surprisingly we have found that it is possible to prepare polyurethaneswith a high level of aromatic polyisocyanate content as well as a lowNMP content and yet maintain good processability with low levels ofsediment to give dispersions that may form hard and resistant coatings.

According to the present invention there is provided an aqueouscomposition with a sediment content ≦5%, comprising a polyurethanedispersion and containing ≦5 wt % of 1-methyl-2-pyrrolidinone by weightof the polyurethane, wherein the polyurethane has an acid value in therange of from 25 to 65 mgKOH/g and is obtained by the reaction of:

-   -   A) an isocyanate-terminated prepolymer formed from components        comprising:        -   (i) 36 to 60 wt % of at least one aromatic polyisocyanate;        -   (ii) 0 to 30 wt % of at least one aliphatic polyisocyanate;        -   (iii) 0 to 15 wt % of at least one isocyanate-reactive            polyol bearing ionic and/or potentially ionic            water-dispersing groups with a weight average molecular            weight ≦500 g/mol;        -   (iv) 0 to 10 wt % of at least one isocyanate-reactive polyol            bearing non-ionic water-dispersing groups;        -   (v) 0 to 15 wt % of at least one isocyanate-reactive polyol            with a weight average molecular weight ≦500 g/mol not            comprised by (iii) or (iv);        -   (vi) 20 to 58 wt % of at least one isocyanate-reactive            polyol not comprised by (iii), (iv) or (v);        -   where (i)+(ii)+(iii)+(iv)+(v)+(vi) add up to 100 wt %;        -   where the NCO/OH ratio is in the range of from 1.2:1 to            2.5:1; and    -   B) at least one active-hydrogen chain extending compound;    -   where the active hydrogen/NCO ratio is in the range of from        0.4:1 to 1.3:1; in the presence of (a) ≦5 wt % of        1-methyl-2-pyrrolidinone by weight of polyurethane ; and (b) at        least one reactive diluent.

Preferably the aqueous composition comprising a polyurethane dispersioncontains ≦3 wt %, more preferably ≦1 wt %, most preferably ≦0.5 wt % andespecially 0 wt % of NMP by weight of the polyurethane.

For clarity by weight of polyurethane is meant the weight ofpolyurethane solids excluding the reactive diluent.

According to a second embodiment of the present invention there isprovided an aqueous composition with a sediment content ≦5%, comprisinga polyurethane vinyl hybrid dispersion and containing ≦0.5 wt % of1-methyl-2-pyrrolidinone by weight of the composition;

-   -   wherein the polyurethane has an acid value in the range of from        25 to 65 mgKOH/g and is obtained by the reaction of:    -   A) an isocyanate-terminated prepolymer formed from components        comprising:        -   (i) 36 to 60 wt % of at least one aromatic polyisocyanate;        -   (ii) 0 to 30 wt % of at least one aliphatic polyisocyanate;        -   (iii) 0 to 15 wt % of at least one isocyanate-reactive            polyol bearing, ionic and/or potentially ionic            water-dispersing groups with a weight average molecular            weight ≦500 g/mol;        -   (iv) 0 to 10 wt % of at least one isocyanate-reactive polyol            bearing non-ionic water-dispersing groups;        -   (v) 0 to 15 wt % of at least one isocyanate-reactive polyol            with a weight average molecular weight ≦500 g/mol not            comprised by (iii) or (iv);        -   (vi) 20 to 58 wt % of at least one isocyanate-reactive            polyol not comprised by (iii), (iv) or (v);        -   where (i)+(ii)+(iii)+(iv)+(v)+(vi) add up to 100 wt %;        -   where the NCO/OH ratio is in the range of from 1.2:1 to            2.5:1; and    -   B) at least one active-hydrogen chain extending compound;    -   where the active hydrogen/NCO ratio is in the range of from        0.4:1 to 1.3:1; in the presence of (a) ≦5 wt % of        1-methyl-2-pyrrolidinone by weight of polyurethane and (b) at        least one reactive diluent.

Preferably components (i)+(ii)+(iii)+(v) add up to ≧42 wt % morepreferably ≧46 wt % and especially ≧50 wt %.

Preferably the composition of the invention contains 0 wt % of NMP.

By a polyurethane vinyl hybrid is meant that a vinyl polymer is preparedby the polymerisation of vinyl monomers in the presence of thepolyurethane. The vinyl polymer may be grafted to the polyurethane oralternatively the vinyl polymer is not grafted to the polyurethaneduring the polymerisation.

For clarity the terms polyurethane, vinyl polymer, vinyl monomer andpolyurethane vinyl hybrid are intended to cover the singular as well asthe plural. Preferably the ratio of polyurethane to vinyl polymer in thepolyurethane vinyl hybrid is in the range of from 95:5 to 30:70, morepreferably 85:15 to 35:65 and most preferably 75:25 to 40:60.

Preferably the acid value of the polyurethane is in the range of from 29to 55 mgKOH/g, more preferably 30 to 55 mgKOH/g and most preferably 31to 53 mgKOH/g of polyurethane.

The aromatic polyisocyanate component (i) can be a mixture of aromaticpolyisocyanates. This term (for the sake of clarity) being intended tomean compounds in which all of the isocyanate groups are directly bondedto an aromatic group, irrespective of whether aliphatic groups are alsopresent. Examples of suitable aromatic polyisocyanates include but arenot limited to p-xylylene diisocyanate, 1,4-phenylene diisocyanate,2,4-toluene diisocyanate, 2,6-toluene diisocyanate, 4,4′-methylenebis(phenyl isocyanate), polymethylene polyphenyl polyisocyanates,2,4′-methylene bis(phenyl isocyanate) and 1,5-naphthylene diisocyanate.

Preferably the isocyanate-terminated prepolymer comprises 36 to 50 wt %,more preferably 37 to 46 wt % of component (i).

Preferably component (i) comprises methylene bis(phenyl isocyanate) (allisomers) and/or toluene diisocyanate (all isomers). More preferablycomponent (i) comprises from 10 to 70 wt % of toluene diisocyanate andfrom 90 to 30 wt % of methylene bis(phenyl isocyanate). Even morepreferably component (i) comprises from 25 to 60 wt % of toluenediisocyanate and from 75 to 40 wt % of methylene bis(phenyl isocyanate)where preferably the methylene bis(phenyl isocyanate) is a mixture of4,4′ and 2,4′-methylene bis(phenyl isocyanate), where the mixturepreferably contains from 5 to 70 wt % of 2,4′-methylene bis(phenylisocyanate).

The aliphatic polyisocyanate component (ii) can be a mixture ofaliphatic isocyanates. This term (for the sake of clarity) beingintended to mean compounds in which all of the isocyanate groups aredirectly bonded to aliphatic or cycloaliphatic groups, irrespective ofwhether aromatic groups are also present.

Examples include but are not limited to ethylene diisocyanate,para-tetramethylxylene diisocyanate (p-TMXDI), meta-tetramethylxylenediisocyanate (m-TMXDI), 1,6-hexamethylene diisocyanate, isophoronediisocyanate, cyclohexane-1,4-diisocyanate and 4,4′-dicyclohexylmethanediisocyanate.

Preferably the isocyanate-terminated prepolymer comprises 0 to 12 wt %,more preferably 0 wt % of component (ii).

Preferably at least 70 wt %, more preferably at least 85 wt % and mostpreferably at least 95 wt % of the polyisocyanates in components (i) and(ii) have two isocyanate groups.

Aromatic or aliphatic polyisocyanates which have been modified by theintroduction of urethane, allophanate, urea, biuret, uretonimine,urethdione or isocyanurate residues can be used for components (i) and(ii) respectively.

The isocyanate-reactive components (iii) to (vi) will normally consistof a polyol component bearing isocyanate-reactive groups which may alsobear other reactive groups. By a polyol component it is also meant toinclude compounds with one or more isocyanate-reactive groups such as—OH, —SH, —NH— and —NH₂.

Water-dispersing groups are preferably introduced by employing at leastone isocyanate-reactive compound bearing a non-ionic and/or ionicwater-dispersing groups as a component in the preparation of theisocyanate-terminated prepolymer. Preferably component (iii) comprisesanionic or potentially anionic water-dispersing groups. Examples ofcompounds bearing anionic water-dispersing groups include phosphoricacid groups, sulphonic acid groups and/or carboxylic acid groups such ascarboxyl group containing diols and triols. Preferably component (iii)comprises dihydroxy alkanoic acids such as 2,2-dimethylolpropionic acid(DMPA) and/or 2,2-dimethylolbutanoic acid (DMBA).

The anionic water-dispersing groups are preferably fully or partially inthe form of a salt. Conversion of for example a potentially anionicwater-dispersing group to the salt form (i.e. anionic water-dispersinggroup) may be effected by neutralisation with a base, preferably duringthe preparation of the aqueous composition of the present invention. Ifthe anionic water-dispersing groups are neutralised, the base used toneutralise the groups may be selected from ammonia, an amine, aninorganic base and combinations thereof. Preferably ammonia andinorganic bases are only used in combination with other neutralisingagents, where generally less than 0.5 equivalent, more preferably lessthan 0.2 equivalent of ammonia and/or inorganic base per anionic, morepreferably per carboxylic acid group is used. Tertiary amines arepreferred. Tertiary amines include for example triethylamine, dimethylamino ethyl methacrylate or oxygen containing amines. Preferably ≧60 wt%, more preferably ≧80 wt % and especially 100 wt % of the polyurethaneis neutralised with an oxygen containing amine.

Preferably the oxygen containing amine is selected from the groupconsisting of N-ethyl morpholine; N-methyl morpholine; and R¹(R²)NR³OHwith a Mn in the range of from 88 to 118, where R, R₂ and R₃ are eachindependently C₁ to C₄-alkyl (for example dimethyl isopropanol amine);and preferably the oxygen containing amine is N,N-dimethylethanolamine.Suitable inorganic bases include alkali hydroxides and carbonates, forexample lithium hydroxide, sodium hydroxide or potassium hydroxide. Aquaternary ammonium hydroxide, for example N⁺(CH₃)₄(OH), can also beused. Generally a base is used which gives counter ions that may bedesired for the composition. For example, preferred counter ions includeLi⁺, Na⁺, K⁺, NH₄ ⁺ and substituted ammonium salts. When inorganic basesare used they are preferably used in combination with at least onetertiary amine as described above.

Neutralisation is usually based on the equivalent of ionic groups, andpreferably the ionic water-dispersing groups in theisocyanate-terminated prepolymer are neutralised with a neutralisingagent in the range of from 0.5:1 to 1.4:1, more preferably 0.6:1 to1.4:1, most preferably 0.75:1 to 1.30:1 and especially 0.95:1 to 1.25:1.At lower levels not enough of the prepolymer is dispersed leading to anincrease in sediment levels and at higher levels an increase in pH mayoccur, resulting in more isocyanate groups reacting with water. Thisresults in an increase in foam and a reduction in the molecular weightof the polyurethane. Additionally at higher levels a discoloration ofthe resultant coating or substrate may occur especially when applied tocertain types of wood such as oak.

Cationic water-dispersible groups can also be used, but are lesspreferred. Examples include pyridine groups, imidazole groups and/orquaternary ammonium groups which may be neutralised or permanentlyionised (for example with dimethylsulphate).

Preferably the isocyanate-terminated prepolymer comprises 2 to 14 wt %,more preferably 5.0 to 13.0 wt % and especially 0.7 to 13 wt % ofcomponent (iii).

Component (iv) bears non-ionic water-dispersing groups. Preferrednon-ionic water-dispersing groups are polyalkylene oxide groups whereethylene oxide is the major component. A small part of the polyethyleneoxide segments can be replaced by propylene oxide segments and/orbutylene oxide segments, however the polyalkylene oxide group shouldstill contain ethylene oxide as a major component. Most preferably thenon-ionic water-dispersing group comprises at least 90 wt %, morepreferably at least 95 wt %, especially at least 98 wt % and mostespecially 100 wt % of ethylene oxide. When the water-dispersible groupis polyethylene oxide, preferably the polyethylene oxide group has amolecular weight from 175 to 5000 Daltons, more preferably from 350 to2200 Daltons, most preferably from 660 to 1600 Daltons.

Examples of preferred compounds bearing non-ionic water-dispersinggroups include methoxy polyethylene glycol (MPEG) with molecular weightsof for example 350, 550, 750, 1000 and 2000, as described in EP 0317258.

An excess of isocyanate-reactive polyols bearing non-ionicwater-dispersing groups may result in lower König Hardness and lowerchemical or stain resistance of a resultant coating. Preferably theisocyanate-terminated prepolymer comprises 0 to 7 wt %, more preferably0 wt % of component (iv).

Examples of component (v) include but are not limited to ethyleneglycol, neopentyl glycol, 1,4-cyclohexyldimethanol and less preferablywater. Also included are low molecular weight polyester polyols whichinclude hydroxyl-terminated reaction products of polyhydric alcoholssuch as ethylene glycol, propylene glycol, diethylene glycol, neopentylglycol, 1,4-butanediol, 1,6-hexanediol, furan dimethanol, cyclohexanedimethanol, glycerol, trimethylolpropane or mixtures thereof, withpolycarboxylic acids, especially dicarboxylic acids or theirester-forming derivatives, for examples succinic, glutaric and adipicacids or their methyl esters, phthalic anhydrides or dimethylterephthalate. Polyesters obtained by the polymerisation of lactones,for example caprolactone in conjunction with a polyol may also be used.

Preferably component (v) has an average of 1.8 to 2.5isocyanate-reactive groups and more preferably component (v) has twohydroxy functional groups.

Preferably the weight average molecular weight of component (v) is inthe range of from 62 to 300 and more preferably 84 to 200 g/mol.

Preferably the isocyanate-terminated prepolymer comprises 2 to 8 wt %,more preferably 3 to 6 wt % of component (v).

Examples of component (vi) include but are not limited to highermolecular weight examples of the compounds listed for component (v),such as polyesters, polyether polyols, polyesteramides, polythioethers,polycarbonates, polyacetals, polyolefins and/or polysiloxanes.

Polyesteramides may be obtained by the inclusion of amino-alcohols suchas ethanolamine in polyesterification mixtures. Polyesters whichincorporate carboxy groups may be used, for example polyesters whereDMPA and/or DMBA is used, provided that the esterification is carriedout under conditions which allow the retention of the carboxyfunctionality in the final polyester.

A feature of such carboxy functional polyesters is that they cancontribute to the dispersibility of the isocyanate-terminated prepolymerin water, thus allowing a lower level of component (iii) to be used.

Polyether polyols which may be used include products obtained by thepolymerisation of a cyclic oxide, for example a minor amount of ethyleneoxide, propylene oxide or tetrahydrofuran or by the addition of one ormore such oxides to polyfunctional initiators, for example water,methylene glycol, ethylene glycol, propylene glycol, diethylene glycol,cyclohexane dimethanol, glycerol, trimethylopropane, pentaerythritol orBisphenol A. Especially useful polyether polyols includepolyoxypropylene diols and triols, poly (oxyethylene-oxypropylene) diolsand triols obtained by the simultaneous or sequential addition ofethylene and propylene oxides to appropriate initiators andpolytetramethylene ether glycols obtained by the polymerisation oftetrahydrofuran. Particularly preferred are polyether diols. For claritythe presence of any ethylene oxide in such polyols is not be enough forthem to be considered as non-ionic water dispersing polyols.

Components (v) and (vi) may also include crosslinking groups.Crosslinking groups are well known in the art and include groups whichmay crosslink at ambient temperature (22±3° C.) by a number ofmechanisms including but not limited to autoxidation (for example byfatty acid groups containing unsaturated bonds); Schiff basecrosslinking (for example the reaction of carbonyl functional groupswith carbonyl reactive amine and/or hydrazine functional groups); silanecrosslinking (for example the reaction of alkoxy silane groups in thepresence of water) and epoxy groups crosslinking with epoxy-reactivefunctional groups.

When an isocyanate-terminated prepolymer is prepared, it isconventionally formed by reacting a stoichiometric excess of the organicpolyisocyanate (components (i) and (ii)) with the isocyanate-reactivecompounds (components (iii), (iv), (v) and (vi)) under substantiallyanhydrous conditions at a temperature between about 30° C. and about130° C. until reaction between the isocyanate groups and theisocyanate-reactive groups is substantially complete; preferably thereactants for the prepolymer are generally used in proportionscorresponding to a ratio of isocyanate groups to isocyanate-reactivegroups of from about 1.4:1 to about 2.0:1 and more preferably from about1.45:1 to 1.75:1.

Preferably the practical NCO % of the prepolymer at the end ofprepolymer preparation should be equal to or less than the theoreticalNCO %. If the practical NCO % is greater than the theoretical NCO %,then the prepolymer reaction has not been completed which will affectthe reproducibility of the dispersion ability since the amount ofresidual free polyols and/or isocyanates may vary. Additionally, if theprepolymer reaction has not been completed and dispersion is started thedispersability will be decreased as any unreacted polyols and freeisocyanates reduce the water up take and will therefore result in moresediment.

If desired, catalysts such as dibutyltin dilaurate and stannous octoate,zirconium or titanium based catalysts may be used to assist thepolyurethane formation. Preferably no catalyst is used.

Active hydrogen-containing chain extending compounds, which may bereacted with the isocyanate-terminated prepolymer includeamino-alcohols, primary or secondary diamines or polyamines, hydrazineand substituted hydrazines.

Examples of such chain extending compounds useful herein includealkylene diamines such as ethylene diamine and cyclic amines such asisophorone diamine. Also compounds such as hydrazine, azines such asacetone azine, substituted hydrazines such as, for example, dimethylhydrazine, 1,6-hexamethylene-bis-hydrazine, carbodihydrazine, hydrazidesof dicarboxylic acids and sulphonic acids such as adipic aciddihydrazide, oxalic acid dihydrazide, isophthalic acid dihydrazide,hydrazides made by reacting lactones with hydrazine, bis-semi-carbazide,and bis-hydrazide carbonic esters of glycols may be useful. Water itselfmay be effective as an indirect chain extending compound. Anothersuitable class of chain extending compounds are the so-called“Jeffamine” compounds with a functionality of 2 or 3 (available fromHuntsman). These are PPO or PEO-based di or triamines, e.g. “Jeffamine”T403 and “Jeffamine” D-400.

Preferably the ratio of active-hydrogen chain extending compound otherthan water to isocyanate (NCO) groups is in the range of from 0.5:1 to1.2:1, more preferably 0.6:1 to 1.1:1, especially 0.75:1 to 1.02:1 andmost preferably 0.78:1 to 0.98:1.

Where the chain extender is other than water, for example a polyamine orhydrazine, it may be added to an aqueous dispersion of theisocyanate-terminated prepolymer or preferably, it may already bepresent in the aqueous medium when the isocyanate-terminated prepolymeris dispersed therein.

The isocyanate-terminated prepolymer may be dispersed in water usingtechniques well known in the art.

Preferably, the isocyanate-terminated prepolymer is added to the waterwith agitation or, alternatively, water may be stirred into theisocyanate-terminated prepolymer.

The reactive diluent is added before and/or during and/or after theformation of the isocyanate-terminated prepolymer to control theviscosity. Suitable reactive diluents which may be used include mono orpolyunsaturated vinyl monomers, which may be polymerised in situ toprepare a vinyl polymer. Other reactive diluents include multifunctionalmaterials well known in the art such as multifunctional (meth)acrylatemonomers, for example (meth)acrylic acid esters of di- and tri- hydroxylalcohols (e.g. polyethylene glycol, polypropylene glycol, aliphaticdiols, neopentyl glycol, ethoxylated bisphenol A, trimethylolpropane,pentaerythritol, glycerol, di-trimethylolpropane, hydroxyl functionalpolyesters, dipentaerythritol and the ethoxylated, propoxylated andpolycaprolactone analogues of all the above); esters of (meth)acrylicacid with monohydric and polyhydric compounds such as ethyl, butyl,hexyl, octyl, and decyl (meth)acrylates; neopentyl glycoldi(meth)acrylate, trimethylolpropane tri(meth)acrylate (TMPTA),pentaerythritol tri(meth)acrylate and tetra(meth)acrylate, caprolactone(meth)acrylates, alkoxylated (meth)acrylates, glycerol (meth)acrylates,1,4-butanediol di(meth)acrylate, 1,6-hexane diol di(meth)acrylate,2,2-dimethyl-3-hydroxypropyl-2,2-dimethyl-3-hydroxypropionatedi(meth)acrylate, isobornyl (meth)acrylate, tripropylene glycoldi(meth)acrylate, urethane (meth)acrylates, (meth)acrylated epoxides andthe like.

Additional vinyl monomers as described herein may also be added to theaqueous phase before and/or during and/or after dispersing theisocyanate-terminated prepolymer in water. The function of theseadditional vinyl monomers is not as a diluent to control the viscosityof the isocyanate-terminated prepolymer formation but to contribute tothe in-situ preparation of a vinyl polymer.

All of the vinyl monomer (comprising the reactive diluent as well as theadditional vinyl monomer) may be present before commencement of vinylpolymerisation, or the additional vinyl monomer may be added to thereaction medium during the course of the vinyl polymerisation (in one ormore stages or continuously). For example, when the aqueous dispersionof the isocyanate-terminated prepolymer is formed in the process to makethe polyurethane as described above some or all of the vinyl monomer maybe added before and/or after and/or during the isocyanate-terminatedprepolymer preparation prior to its dispersion into water (and thereforemay act as a reactive diluent). Some or all of the vinyl monomer mayhave already been added to the water prior to the dispersion of theisocyanate-terminated prepolymer therein.

Preferably the reactive diluent comprises between 5 and 40%, morepreferably between 5 and 35%, most preferably between 10 and 32% andespecially between 15 to 30% by weight of both the isocyanate-terminatedprepolymer and the reactive diluent together. Increasing the level ofreactive diluent may result in an increase of the sediment content.

Preferably the reactive diluent comprises at least 80 wt %, morepreferably at least 95 wt % and most preferably 100 wt % ofα,β-mono-unsaturated vinyl monomers based on the total weight of vinylmonomers used.

Examples of vinyl monomers include but are not limited to 1,3-butadiene,isoprene; trifluoro ethyl (meth)acrylate (TFEMA); dimethyl amino ethyl(meth)acrylate (DMAEMA); styrene, α-methyl styrene, (meth)acrylic amidesand (meth)acrylonitrile; vinyl halides such as vinyl chloride;vinylidene halides such as vinylidene chloride; vinyl ethers; vinylesters such as vinyl acetate, vinyl propionate, vinyl laurate; vinylesters of versatic acid such as VeoVa 9 and VeoVa 10 (VeoVa is atrademark of Resolution); heterocyclic vinyl compounds; alkyl esters ofmono-olefinically unsaturated dicarboxylic acids such as di-n-butylmaleate and di-n-butyl fumarate and in particular, esters of acrylicacid and methacrylic acid of formula CH₂═CR⁴—COOR⁵ wherein R⁴ is H ormethyl and R⁵ is optionally substituted alkyl or cycloalkyl of 1 to 20carbon atoms (more preferably 1 to 8 carbon atoms) examples of which aremethyl methacrylate, ethyl methacrylate, n-butyl (meth)acrylate (allisomers), octyl (meth)acrylate (all isomers), 2-ethylhexyl(meth)acrylate, isopropyl (meth)acrylate and n-propyl (meth)acrylate.Preferred monomers of formula CH₂═CR⁴—COOR⁵ include butyl (meth)acrylate(all isomers), methyl (meth)acrylate, octyl (meth)acrylate (all isomers)and ethyl (meth)acrylate. Particularly preferably the reactive diluentcomprises 40 to 100 wt % of vinyl monomer selected from the groupconsisting of methylmethacrylate and ethylmethacrylate. Most preferablythe reactive diluent added before and/or during and/or after theformation of the iscocyante-terminated prepolymer to control theviscosity comprises <45 wt %, more preferably <40 wt % of styrene andstyrene based vinyl monomers (such as α-methyl styrene). The presence ofhydrophobic monomers such as styrene decreases the ease of dispersion ofthe prepolymer in water which results in an increase in the sedimentcontent.

The vinyl monomers may include vinyl monomers carrying functional groupssuch as crosslinker groups and/or water-dispersing groups. Suchfunctionality may be introduced directly in the vinyl polymer byfree-radical polymerisation, or alternatively the functional group maybe introduced by a reaction of a reactive vinyl monomer, which issubsequently reacted with a reactive compound carrying the desiredfunctional group.

Vinyl monomers providing ionic or potentially ionic water-dispersinggroups which may be used as additional vinyl monomers include but arenot limited to (meth)acrylic acid, itaconic acid, maleic acid,citraconic acid and styrenesulphonic acid.

Preferably the level of vinyl monomers providing ionic or potentiallyionic water-dispersing groups is between 0 to 5 wt %, more preferablybetween 0 and 1 wt % and most preferably 0 wt % of the total level ofvinyl monomers used.

Preferably the resultant vinyl polymer has an acid value in the range offrom 0 to 20, more preferably 0 to 10 and especially 0 mgKOH/g.

Vinyl monomers providing non-ionic water-dispersing groups includealkoxy polyethylene glycol (meth)acrylates, preferably having a numberaverage molecular weight of from 350 to 3000. Examples of such monomerswhich are commercially available include ω-methoxypolyethylene glycol(meth)acrylates.

Examples of suitable vinyl monomers providing crosslinking groupsinclude acrylic and methacrylic monomers having at least one freecarboxyl or hydroxyl group (if used as an additional vinyl monomer),epoxy, acetoacetoxy or carbonyl group, such as acrylic acid andmethacrylic acid, glycidyl acrylate, glycidyl methacrylate, acetoacetoxy ethyl methacrylate, allyl methacrylate, tetraethylene glycoldimethacrylate, divinyl benzene and diacetone acrylamide.

Preferably the weight average molecular weight (Mw) of the resultantvinyl polymer is at least 60,000 Daltons, more preferably in the rangeof fro m 100,000 to 6,000,000 Daltons and most preferably in the rangeof from 150,000 to 2,500,000 Daltons.

The Tg of a polymer herein stands for the glass transition temperatureand is well known to be the temperature at which a polymer changes froma glassy, brittle state to a rubbery state. Tg values of polymers may bedetermined experimentally using techniques such as Differential ScanningCalorimetry (DSC) or calculated theoretically using the well-known Foxequation where the Tg (in Kelvin) of a copolymer having “n”copolymerised comonomers is given by the weight fractions “W” and the Tgvalues of the respective homopolymers (in Kelvin) of each comonomer typeaccording to the equation“1/Tg=W ₁ /Tg ₁ +W ₂ /Tg ₂ + . . . W _(n) /Tg _(n)”.

The calculated Tg in Kelvin may be readily converted to ° C.

The calculated Tg of the resultant vinyl polymer in the polyurethanevinyl hybrid is preferably in the range of from 20 to 120° C. and morepreferably 30 to 110° C. If the resultant vinyl polymer comprises morethan one stage, then preferably the Tg is the calculated Tg of theaverage resultant vinyl polymer and is in the range of from −20 to 125°C., more preferably 5 to 120° C. and most preferably 30 to 110° C.

The weight average particle size, assuming a substantially sphericalparticle shape, of the particles in the polyurethane or polyurethanevinyl hybrid dispersion is preferably less than 500 nm, more preferablyin the range of from 20 to 300 nm and most preferably in the range offrom 20 to 200 nm. More preferably at least 60 wt %, more preferably atleast 75 wt % and most preferably at least 85 wt % of the particles havea particle size less than 500 nm. A disadvantage of a particle sizegreater than 500 nm is that the sediment content may be increasedresulting in unacceptable processing.

The polymerisation of the vinyl monomers may be carried out as a batch,step-wise, gradient or as a semi-continuous polymerisation process tomake a single or a multistage vinyl polymer.

Free-radical polymerisation of vinyl monomers will require the use of afree-radical-yielding initiator to initiate the vinyl polymerisation.Suitable free-radical-yielding initiators include hydrogen peroxide;percarbonates; organic peroxides, such as acyl peroxides includingbenzoyl peroxide, alkyl hydroperoxides such as t-butyl hydroperoxide(tBHPO) and cumene hydroperoxide; dialkyl peroxides such as di-t-butylperoxide; peroxy esters such as t-butyl perbenzoate and the like;mixtures may also be used. The peroxy compounds are in some casesadvantageously used in combination with suitable reducing agents (redoxsystems) such as Na or K pyrosulphite or bisulphite, and iso-ascorbicacid. Metal compounds such as Fe.EDTA (EDTA is ethylene diaminetetracetic acid) may also be usefully employed as part of the redoxinitiator system. Azo functional initiators may also be used. Preferredazo initiators include azobis(isobutyronitrile) and4,4′-azobis(4-cyanovaleric acid). The amount of initiator or initiatorsystem used is conventional, e.g. within the range 0.05 to 6 wt % basedon the total weight of vinyl monomers used. Preferred initiators includeazobis(isobutyronitrile) and/or 4,4′-azobis(4-cyanovaleric acid) andredox couples that are active between 30° C. and 75° C. Most preferredinitiators are redox couples that are active between 30° C. and 75° C.such as tBHPO and isoascorbic acid.

Molecular weight control may be provided by catalytic chain transferagents or may be provided by using chain transfer agents such asmercaptans and halogenated hydrocarbons, for example mercaptans such asn-dodecylmercaptan, n-octylmercaptan, t-dodecylmercaptan,mercaptoethanol, iso-octyl thioglycolate, C₂ to C₈ mercapto carboxylicacids and esters thereof and halogenated hydrocarbons such as carbontetrabromide and bromotrichloromethane.

Combinations of conventional chain transfer agents and catalytic chaintransfer agents may also be used.

Surfactants can be utilised in order to assist in the dispersion of thepolyurethane and/or vinyl polymer in water (even if they areself-dispersible). Suitable surfactants include but are not limited toconventional anionic, cationic and/or non-ionic surfactants and mixturesthereof. Anionic and/or non-ionic surfactants are preferred. The amountof surfactant used is preferably 0 to 6% by weight, more preferably 0 to3% by weight and especially 0.1 to 2% by weight based on the weight ofthe solids in the aqueous composition of the invention.

In a third embodiment of the present invention there is provided aprocess for making an aqueous composition with a sediment content ≦5%,comprising a polyurethane dispersion and containing ≦5 wt % of1-methyl-2-pyrrolidinone by weight of the polyurethane, wherein thepolyurethane has an acid value in the range of from 25 to 65 mgKOH/g,and where the process is carried out in steps comprising:

-   -   I: reacting in the presence of (a) ≦5 wt % of        1-methyl-2-pyrrolidinone by weight of polyurethane and (b) at        least one reactive diluent;        -   (i) 36 to 60 wt % of at least one aromatic polyisocyanate;        -   (ii) 0 to 30 wt % of at least one aliphatic polyisocyanate;        -   (iii) 0 to 15 wt % of at least one isocyanate-reactive            polyol bearing ionic and/or potentially ionic            water-dispersing groups with a weight average molecular            weight ≦500 g/mol;        -   (iv) 0 to 10 wt % of at least one isocyanate-reactive polyol            bearing non-ionic water-dispersing groups;        -   (v) 0 to 15 wt % of at least one isocyanate-reactive polyol            with a weight average molecular weight ≦500 g/mol not            comprised by (iii) or (iv);        -   (vi) 20 to 58 wt % of at least one isocyanate-reactive            polyol not comprised by (iii), (iv) or (v);        -   where (i)+(ii)+(iii)+(iv)+(v)+(vi) add up to 100 wt %;        -   where the NCO/OH ratio is in the range of from 1.2:1 to            2.5:1 to form an isocyanate-terminated prepolymer;    -   II: neutralising the isocyanate-terminated prepolymer with a        neutralising agent;    -   III: forming an aqueous dispersion of the isocyanate-terminated        prepolymer in water;    -   IV: reacting the isocyanate-terminated prepolymer with at least        one active hydrogen chain-extending compound to form the        polyurethane;    -   where the active hydrogen/NCO ratio is in the range of from        0.4:1 to 1.3:1;    -   VI: polymerising the reactive diluent.

In a fourth embodiment of the present invention there is provided aprocess for making an aqueous composition with a sediment content ≦5%,comprising a polyurethane vinyl hybrid dispersion and containing ≦0.5 wt% of 1-methyl-2-pyrrolidinone by weight of the composition, wherein thepolyurethane has an acid value in the range of from 25 to 65 mgKOH/g,and where the process is carried out in steps comprising:

-   -   I: reacting in the presence of (a) ≦5 wt % of        1-methyl-2-pyrrolidinone by weight of polyurethane and (b) at        least one reactive diluent;        -   (i) 36 to 60 wt % of at least one aromatic polyisocyanate;        -   (ii) 0 to 30 wt % of at least one aliphatic polyisocyanate;        -   (iii) 0 to 15 wt % of at least one isocyanate-reactive            polyol bearing ionic and/or potentially ionic            water-dispersing groups with a weight average molecular            weight ≦500 g/mol;        -   (iv) 0 to 10 wt % of at least one isocyanate-reactive polyol            bearing non-ionic water-dispersing groups;        -   (v) 0 to 15 wt % of at least one isocyanate-reactive polyol            with a weight average molecular weight ≦500 g/mol not            comprised by (iii) or (iv);        -   (vi) 20 to 58 wt % of at least one isocyanate-reactive            polyol not comprised by (iii), (iv) or (v);        -   where (i)+(ii)+(iii)+(iv)+(v)+(vi) add up to 100 wt %;        -   where the NCO/OH ratio is in the range of from 1.2:1 to            2.5:1 to form an isocyanate-terminated prepolymer;    -   II: neutralising the isocyanate-terminated prepolymer with a        neutralising agent;    -   III: forming an aqueous dispersion of the isocyanate-terminated        prepolymer in water;    -   IV: reacting the isocyanate-terminated prepolymer with at least        one active hydrogen chain-extending compound to form the        polyurethane;    -   where the active hydrogen/NCO ratio is in the range of from        0.4:1 to 1.3:1;    -   V: adding additional vinyl monomer; and    -   VI: polymerising the reactive diluent and vinyl monomer added in        step V.

The process steps may be carried out in a number of variations. Forexample step II may be carried out simultaneously with or before stepIII. Steps II, III and IV may be carried out simultaneously. Steps II,III, IV and V may be carried out simultaneously. Steps II, III, IV, Vand VI may be carried out simultaneously. Step V may be carried out atany phase of the process. Preferably step II is not carried out afterstep III or step IV. Preferably step III is not carried out after StepIV. Preferably Step VI is not carried out before Step III. Step VI maybe carried out during and/or after Step III. Step II may be carried outsimultaneously with step III and the neutralising agent is substantiallypresent in the water.

Step II, step III and/or step IV may be carried out by means of anin-line mixer. If an in-line mixer is used, preferably at least Step IIis carried out by means of an in-line mixer. The time between step IIIand step IV is preferably less than 40 minutes, more preferably lessthan 15 minutes, especially less than 5 minutes and most preferably StepIII and Step IV are carried out simultaneously. Preferably at least 50wt % of the active-hydrogen chain extending compound is present in thewater before completion of step III. Step VI may be carried out by meansof a batch polymerisation process.

The aqueous composition of the invention typically has a solids contentof from about 20 to 55% by weight, more usually from 25 to 45% by weightand especially from 29 to 39% by weight.

The aqueous composition of the invention is particularly useful forproviding the principle component of coating compositions (e.g.protective or decorative coating compositions) especially for coatingcompositions for floors, for which purpose it may be further dilutedwith water and/or organic solvents, or it may be supplied in a moreconcentrated form by evaporation of water and/or organic components ofthe liquid medium. As a coating composition, it may be applied to avariety of substrates including wood (in particular porous wood), board,metals, stone, concrete, glass, cloth, leather, paper plastics, foam andthe like, by any conventional method including brushing, dipping, flowcoating, spraying and the like. The aqueous composition once applied maybe allowed to dry naturally at ambient temperature or the drying processmay be accelerated by the application of heat.

The aqueous composition of the invention may contain conventionalingredients, some of which have been mentioned above; examples includepigments (for example titanium dioxide, iron oxide, chromium basedcompounds and/or metal pthalocyanine compounds), dyes, emulsifiers,surfactants, plasticisers, thickeners, heat stabilisers, matting agentssuch as silica, levelling agents, anti-cratering agents, fillers,sedimentation inhibitors, UV absorbers, antioxidants, drier salts,water-soluble and/or water-insoluble co-solvents, wetting agents,defoamers, fungicides, bacteriocides, waxes and the like introduced atany stage of the production process or subsequently. It is possible toinclude an amount of antimony oxide in the dispersions to enhance thefire retardant properties.

Optionally the isocyanate-terminated prepolymer may be dispersed in apreformed polymer dispersion including vinyl polymer, polyurethane,alkyd, polyurethane vinyl hybrid dispersions and mixtures thereof.

The aqueous composition of the invention preferably contains less than15 wt % and more preferably less than 10 wt % of organic co-solventsbased on the weight of the composition. The aqueous coating compositionof the invention may be substantially co-solvent-free. By asubstantially co-solvent-free aqueous composition is meant that thecomposition must contain less than 1.5 wt % of organic co-solvents basedon total polymer solids, more preferably less than 0.5 wt %, and mostpreferably no organic co-solvent at all.

For substantially co-solvent-free aqueous compositions, which are filmforming at ambient temperature it has been found that an addition of 2to 15 wt %, more preferably 4 to 12 wt % and most preferably 6 to 10 wt% of an organic co-solvent Q based on polymer solids can give animproved level of chemical and stain resistance.

Organic co-solvent Q may optionally be added at any stage of theisocyanate-terminated prepolymer or polyurethane or polyurethane vinylhybrid preparation to control the viscosity.

Organic co-solvent Q has an evaporation rate from 0.001 to 0.1, morepreferably from 0.002 to 0.05 and most preferably from 0.002 to 0.02,relative to butyl acetate with an evaporation rate of 1.0.

Preferably the organic co-solvent Q is selected from the groupconsisting of oxygen containing co-solvents. Especially preferred areethyldiglycol, butyl glycol, butyldiglycol, Dowanol DPnB and Dowanol DPM(Dowanol is a trade mark of Dow).

If desired the aqueous composition of the invention can be used incombination with other polymer compositions which are not according tothe invention.

König Hardness as used herein is a standard measure of hardness, thisbeing a determination of how the viscoelastic properties of a filmformed from the dispersion slows down a swinging motion deforming thesurface of the film and is measured according to DIN 53157 using anErichsen hardness equipment.

Preferably the aqueous composition of the invention, and more preferablythe aqueous composition of the second embodiment of the invention, whenin the form of a film has a König Hardness ≧120s, more preferably ≧130s,most preferably ≧140s, especially ≧160s and especially ≧165s.

Elongation at break as used herein is a measure of the elongation atbreak of an unsupported film (i.e. not on a substrate) and is measuredusing an Instron tensile device and is defined as the maximum elongationuntil break under a constant strain rate.

Preferably the aqueous composition of the invention, and more preferablythe aqueous composition of the second embodiment of the invention, whenin the form of a film has an elongation at break ≧50% and a KönigHardness ≧120s.

Preferably the aqueous composition of the invention containing ≦2 wt %and more preferably 0 wt % of a co-solvent by weight of the composition,has a minimum film forming temperature ≦50° C., more preferably ≦28° C.and especially ≦23° C.

Most preferably the aqueous composition of the invention, and morepreferably the aqueous composition of the second embodiment of theinvention, containing ≦2 wt % of a co-solvent by weight of thecomposition has a minimum film forming temperature ≦50° C. and when inthe form of a film has a König Hardness ≧120s.

The sediment content is determined after preparation of the polyurethanecomposition but before any filtration is carried out.

The aqueous composition of the invention preferably has a sedimentcontent of ≦2.5%, more preferably ≦1%, more preferably ≦0.5% andespecially ≦0.35%.

It is also well known that polyurethanes based substantially on aromaticisocyanates have a tendency to yellow over time. Surprisingly we havefound that polyurethane dispersion of the invention demonstrated asignificant reduction in yellowing when compared to a similar aromaticpolyurethane with high levels of NMP. The yellowness may be determinedby measuring the colour co-ordinates of a film of a composition using aDr Lange Spectro-pen (type LMG161), and ‘b’ is a measure of yellowness(+b) or blueness (−b). The coordinates approach zero for neutral colourssuch as white, grey or black. The higher the values are, the moresaturated a colour is.

The change in yellowness of the resultant film was determined bymeasuring (w) the yellowness of the substrate before UV exposure, (x)the yellowness of the film coated in the substrate before UV exposure,(y) the yellowness of the substrate after UV exposure and (z) theyellowness of the film coated on the substrate after UV exposure.Yellowing (Δb) is defined as ((z)−(y))−((x)−(w)).

Preferably the value of Δb for the composition of the invention is ≦3.0and more preferably ≦2.7.

In a fourth embodiment of the present invention there is provided acoating on a substrate obtained from an aqueous composition as describedherein.

In a fifth embodiment of the present invention is provided a method forcoating a substrate with an aqueous composition as described herein.

In a sixth embodiment of the present invention there is provided the useof an aqueous composition as described herein in an aqueous coatingcomposition.

In a seventh embodiment of the present invention there is provided theuse of an aqueous composition as described herein for coating floors.

The present invention is now illustrated but in no way limited byreference to the following examples. Unless otherwise specified allparts, percentages and ratios are on a weight basis.

Components and abbreviations used:

-   MDI=Isomer mixture of 4,4′-diphenylmethane diisocyanate and    2,4′-diphenylmethane diisocyanate available from Huntsman-   TDI=Isomer mixture of 2,4-toluene diisocyanate and 2,6-toluene    diisocyanate available from Huntsman-   Rubinate 9279=Blend of 41 wt % toluene diisocyanate and 59 wt %    diphenylmethane diisocyanate-   IPDI=Isophorone isocyanate available from Bayer-   DMPA=Dimethylolpropionic acid available from Perstorp polyols-   CHDM=1,4-Cyclohexanedimethanol available from Eastman Chemical bv-   PPG1000=Polypropylene glycol 1000, OH-number=110.5 mg KOH/g    available from Dow Benelux-   Terathane 1000=Polytetramethylene ether glycol, OH-number=112.5 mg    KOH/g available from Du Pont de Nemours-   Priplast 3192=Polyester diol, OH-number=56.0 mg KOH/g available from    Uniqema Chemie bv-   PEC90=Polyester diol, OH-number=120 mg KOH/g available from Durez    Europe-   DMEA=N,N-Dimethylethanolamine available from Chemproha bv-   EDA=Ethylene diamine available from Delamine bv-   Hydrazine=Hydrazine hydrate available from Bayer AG-   Abex2545=Nonionic surfactant available from Rhodia-   Disponyl AFX4060=Nonionic surfactant available from Cognis-   Disponyl AFX4030=Nonionic surfactant available from Cognis-   MMA=Methyl methacrylate available from ECEM European Chemical    Marketing bv-   STY=Styrene available from Dow Benelux nv-   BA=n-Butyl acrylate available from BASF UK Ltd-   BMA=n-Butyl methacrylate available from Arkema Nederland bv-   2-EHA=2-Ethylhexyl acrylate available from Dow Benelux nv-   Ionol cp=2,6-Di-tert-butyl-4-methylphenol available from Avecia Inc-   IAA=Isoascorbic acid available from Brenntag Volkers Benelux bv-   tBHPO=tert-Butyl hydroperoxide, available from Akzo Nobel Chemicals    bv-   FeEDTA=Iron-ethylenediaminetetracetic acid complex, 1% in water-   Dowanol DPM=Di(propylene glycol) monomethyl ether available from Dow    Benelux-   MPEG=Methoxy polyethylene glycol-   DEA=Diethanolamine-   NCO=Isocyanate group-   MFFT=Minimum film forming temperature-   UV=Ultra violet    The specifications for all of the Examples are given in Table 1    below.

EXAMPLE I

Stage 1: Nonionic diol: To 1459.5 g of MPEG 750 (M_(w)=740 g/mole),343.8 g of 2,4-toluene diisocyanate was added over a 90 minute period at40-45 ° C. At the end of the reaction, the isocyanate content was 4.60%.The system was cooled to 25° C. and 196.7 g of DEA was added. Theresultant nonionic diol had an OH number of 103 mg KOH/g.

Stage 2: Polyurethane dispersion: A 2000 cm³ flask equipped with athermometer and overhead stirrer was charged with Rubinate 9279 (511.9g), Ionol cp (0.48 g), MMA (240.0 g) and STY (240.0 g). Then a mixturecontaining CHDM (65.74 g), DMPA (95.20 g), the dispersing non-ionic diolprepared in stage 1 (56.0 g) and Terathane 1000 (391.1 g) was added overa period of 60 minutes. The reaction was allowed to exotherm to 50° C.After the exotherm was complete the reaction was kept at 85° C. for 2hours. The NCO-content of the resultant isocyanate-terminated prepolymerwas 3.98% (theoretical 4.23%).

A dispersion of the isocyanate-terminated prepolymer was made by feeding500 g of the isocyanate-terminated prepolymer over 1 hour to deionisedwater (1064 g) containing DMEA (21.7 g), 15.2% hydrazine (46.9 g) andABEX2545 (10.5 g). The isocyanate-terminated prepolymer temperatureduring dispersion was kept at 50° C. and the dispersion temperature wascontrolled between 25 to 30° C.

Stage 3: Polyurethane Vinyl (50/50) Hybrid Dispersion:

To 1430 g of the dispersion prepared in Stage 2 was charged deionisedwater (386.2 g), MMA (26.1 g), BA (57.9 g) and STY (90.1 g). After theaddition of the additional monomers the dispersion was allowed to stirfor 1 hour at ambient temperature. To the resultant dispersion was addeda 10% tBHPO solution in water (7.9 g) and a 1% FeEDTA solution in water(4.0 g) followed by feeding in a 1% IAA solution in water (60.9 g) overa period of 45 minutes. The resultant polyurethane vinyl hybriddispersion was filtered through 75 micron filter cloths.

EXAMPLE II

Stage 1: Polyurethane dispersion: A 2000 cm³ flask equipped with athermometer and overhead stirrer was charged with Rubinate 9279 (562.4g), Ionol cp (0.4 g) and MMA (369.3 g). Then a mixture containing CHDM(48.4), DMPA (125.5 g) and Terathane 1000 (494.4 g) was added over aperiod of 60 minutes. The reaction was allowed to exotherm to 50° C.After the exotherm was complete the reaction was kept at 85° C. for 2hours. The NCO-content of the isocyanate-terminated prepolymer was 4.47%(theoretical 4.64%).

A dispersion of the isocyanate-terminated prepolymer was made by feeding300 g of the isocyanate-terminated prepolymer at 50° C. over 1 hour todeionised water (851.6 g) containing DMEA (17.20 g), 15.2% hydrazine(29.58 g) and Disponyl AFX4060 (5.77 g). The isocyanate-terminatedprepolymer temperature during dispersion was kept at 50° C. and thedispersion temperature was controlled between 25 to 30° C.

Stage 2: Polyurethane vinyl (50/50) hybrid dispersion: To the dispersionprepared in Stage 1 (1204.2 g) was charged BA (43.9 g) and STY (117.7g). After the addition of the additional vinyl monomers the dispersionwas allowed to stir for 1 hour at ambient temperature. To the resultantdispersion was then added a 10% tBHPO solution in water (6.0 g) and a 1%FeEDTA solution in water (3.0 g) followed by feeding a 1% IAA solutionin water (46.2 g) over a period of 45 minutes. The resultantpolyurethane vinyl hybrid dispersion was filtered through 75 micronfilter cloths.

EXAMPLE III

Stage 1: Polyurethane dispersion: A 2000 cm³ flask equipped with athermometer and overhead stirrer was charged with DMPA (125.5 g), CHDM(48.5 g), PPG1000 (574.2 g), MMA (369.2 g), TDI (482.5 g) and Ionol cp(0.4). The reaction was allowed to exotherm to 50° C. After the exothermwas complete the reaction was kept at 85° C. for 2 hours. TheNCO-content of the isocyanate-terminated prepolymer was 4.80%(theoretical 4.85%).

A dispersion of the isocyanate-terminated prepolymer was made by feeding275 g of the isocyanate-terminated prepolymer at 50° C. over 1 hour todeionised water (782 g) containing DMEA (15.77 g), 15.2% hydrazine(31.43 g) and of Disponyl AFX4060 (10.57 g). The isocyanate-terminatedprepolymer temperature during dispersion was kept at 50° C. and thedispersion temperature was controlled between 25 to 30° C.

Stage 2: Polyurethane vinyl (30/70) hybrid dispersion: To the dispersionprepared in Stage 1 (540 g) was charged deionised water (321.3 g), BA(47.3 g), MMA (42.7 g) and STY (127.0 g). After the addition of theadditional vinyl monomers the dispersion was allowed to stir for 1 hourat ambient temperature. To the resultant dispersion was then added a 10%tBHPO solution in water (6.5 g) and a 1% FeEDTA solution in water (3.2g) followed by feeding a 2.5% IAA solution in water (19.9 g) over aperiod of 45 minutes. The resultant polyurethane vinyl hybrid dispersionwas filtered through 75 micron filter cloths.

EXAMPLE IV

Stage 1: Polyurethane dispersion: A 2000 cm³ flask equipped with athermometer and overhead stirrer was charged with DMPA (96.0 g), CHDM(32.0 g), PPG1000 (622.1 g), MMA (320.0 g), Rubinate 9279 (529.9 g) andIonol cp (0.3 g). The reaction was allowed to exotherm to 50° C. Afterthe exotherm was complete the reaction was kept at 85° C. for 2 hours.The NCO-content of the isocyanate-terminated prepolymer was 4.48%(theoretical 4.92%).

A dispersion of the isocyanate-terminated prepolymer was made by feeding375.0 g of the isocyanate-terminated prepolymer at 50° C. over 1 hour todeionised water (886.6 g) containing Dowanol DPM (79.0 g), DMEA (16.4g), 15.2% hydrazine (37.9 g) and Abex2545 (18.0 g). Theisocyanate-terminated prepolymer temperature during dispersion was keptat 50° C. and the dispersion temperature was controlled between 25 to30° C.

Stage 2: Polyurethane vinyl (60/40) hybrid dispersion: To the dispersionprepared in Stage 1 (1414.7 g) was charged MMA (25.0) and STY (100.0 g).After the addition of the additional vinyl monomers the dispersion wasallowed to stir for 1 hour at ambient temperature. To the resultantdispersion was then added a 10% tBHPO solution in water (5.2 g) and a 1%FeEDTA solution in water (2.6 g) followed by feeding a 2.5% IAA solutionin water (16.0 g) over a period of 45 minutes. The resultantpolyurethane vinyl hybrid dispersion was filtered through 75 micronfilter cloths.

EXAMPLE V

Stage 1: Polyurethane dispersion: A 2000 cm³ flask equipped with athermometer and overhead stirrer was charged with DMPA (122.5 g),Priplast 3192 (489.2 g), MMA (420.0 g), Rubinate 9279 (368.4 g) andIonol cp (0.4). The reaction was allowed to exotherm to 50° C. After theexotherm was complete the reaction was kept at 85° C. for 2 hours. TheNCO-content of the isocyanate-terminated prepolymer was 3.22%(theoretical 3.47%).

A dispersion of the isocyanate-terminated prepolymer was made by feeding500 g of the isocyanate-terminated prepolymer at 50° C. over 1 hour todeionised water (956.9 g) containing DMEA 32.0 g, 15.2% hydrazine (36.3g) and Abex2545 (21.0 g). The isocyanate-terminated prepolymertemperature during dispersion was kept at 50° C. and the dispersiontemperature was controlled between 25 to 30° C.

Stage 2: Polyurethane vinyl (30/70) hybrid dispersion: To the dispersionprepared in Stage 1 (1549.0 g) was charged a 10% tBHPO solution in water(3.90 g) and a 1% FeEDTA solution in water (2.0 g) followed by feeding a2.5 IAA solution in water (12.0 g) over a period of 45 minutes. Theresultant polyurethane vinyl hybrid dispersion was filtered through 75micron filter cloths.

EXAMPLE VI

Stage 1: Polyurethane dispersion: A dispersion of anisocyanate-terminated prepolymer was made by feeding 350 g of theisocyanate-terminated prepolymer described in Example V, Stage 1 at 50°C. over 1 hour to 791.0 g of deionised water containing DMEA (22.4 g),15.2% hydrazine (25.4 g) and Abex2545 (14.7 g). Theisocyanate-terminated prepolymer temperature during dispersion was keptat 50° C. and the dispersion temperature was controlled between 25 to30° C.

Stage 2: Polyurethane vinyl (50/50) hybrid dispersion: To the dispersionprepared in Stage 1 (1204.6 g) was charged 2-EHA (49.0 g) and STY (91.0g). After the addition of the additional vinyl monomers the dispersionwas allowed to stir for 1 hour at ambient temperature. To the resultantdispersion was then added a 10% tBHPO solution in water (6.4 g) and a 1%FeEDTA solution in water (3.2 g) followed by feeding a 2.5% IM solutionin water (19.6 g) over a period of 45 minutes. The resultantpolyurethane vinyl hybrid dispersion was filtered through 75 micronfilter cloths.

EXAMPLE VII

Stage 1: Polyurethane dispersion: A dispersion of theisocyanate-terminated prepolymer was made by feeding 375.0 g of theisocyanate-terminated prepolymer prepared as described in Example IVstage 1 at 50° C. over 1 hour to deionised water (1087.4 g) containingDowanol DPM (79.0 g), DMEA (16.4 g), EDA (10.8 g) and Abex2545 (18.0 g).The isocyanate-terminated prepolymer temperature during dispersion waskept at 50° C. and the dispersion temperature was controlled between 25to 30° C.

Stage 2: Polyurethane vinyl (60/40) hybrid dispersion: To the dispersionprepared in Stage 1 (1506.6 g) was charged BA (25.0) and STY (100.0 g).After the addition of the additional vinyl monomers the dispersion wasallowed to stir for 1 hour at ambient temperature. To the resultantdispersion was then added a 10% tBHPO solution in water (5.2 g) and a 1%FeEDTA solution in water (2.6 g) followed by feeding a 2.5% IM solutionin water (16.0 g) over a period of 45 minutes. The resultantpolyurethane vinyl hybrid dispersion was filtered through 75 micronfilter cloths.

EXAMPLE VIII

Stage 1: Polyurethane dispersion: A 1000 cm³ flask equipped with athermometer and overhead stirrer was charged with DMPA (48.0 g), CHDM(14.4 g), Priplast 3192 (240.6 g), MMA (120.0 g), TDI (177.04 g) andIonol cp (0.1). The reaction was allowed to exotherm to 50° C. After theexotherm was complete the reaction was kept at 85° C. for 2 hours. TheNCO-content of the isocyanate-terminated prepolymer was 5.73%(theoretical 6.15%).

A dispersion of the isocyanate-terminated prepolymer was made by feeding500.0 g of the isocyanate-terminated prepolymer at 50° C. over 1 hour todeionised water (955.9 g) containing DMEA (29.2 g), 15.2% hydrazine(63.2) g and Disponyl AFX4060 (20.0 g). The isocyanate-terminatedprepolymer temperature during dispersion was kept at 50° C. and thedispersion temperature was controlled between 25 to 30° C.

Stage 2: Polyurethane vinyl (80/20) hybrid dispersion: To the dispersionprepared in Stage 1 (1571.2 g) was charged a 10% tBHPO solution in water(2.6 g) and a 1% FeEDTA solution in water (1.3 g) followed by feeding a2.5% IAA solution in water (8.0 g) over a period of 45 minutes. Theresultant polyurethane vinyl hybrid dispersion was filtered through 75micron filter cloths.

EXAMPLE IX

Stage 1: Polyurethane dispersion: A 2000 cm³ flask equipped with athermometer and overhead stirrer was charged with DMPA (91.0 g), CHDM(45.5 g), Terathane 1000 (343.6 g), MMA (390.0 g), Rubinate 9279 (343.9g), IPDI (86.0 g) and Ionol cp (0.4). The reaction was allowed toexotherm to 50° C. After the exotherm was complete the reaction was keptat 88° C. for 2 hours. The NCO-content of the isocyanate-terminatedprepolymer was 3.96% (theoretical 4.33%).

A dispersion of the isocyanate-terminated prepolymer was made by feeding580.0 g of the isocyanate-terminated prepolymer at 50° C. over 45 min todeionised water (1113.6 g) containing DMEA (29.7 g), 15.2% hydrazine(50.7 g) and Disponyl AFX4030 (40.6 g). The isocyanate-terminatedprepolymer temperature during dispersion was kept at 50° C. and thedispersion temperature was controlled between 25 to 30° C.

Stage 2: Polyurethane vinyl (70/30) hybrid dispersion: To the dispersionprepared in Stage 1 (800.0 g) was charged a 10% tBHPO solution in water(2.0 g) and a 1% FeEDTA solution in water (1.0 g) followed by feeding a2.5% IAA solution in water (6.1 g) over a period of 45 minutes. Theresultant polyurethane vinyl hybrid dispersion was filtered through 75micron filter cloths.

EXAMPLE X

Stage 1: Polyurethane dispersion: A dispersion of theisocyanate-terminated prepolymer was made by feeding 580.0 g of theisocyanate-terminated prepolymer described in Example IX at 50° C. over1 hour to deionised water (1113.6 g) containing DMEA (29.7 g), 15.2%hydrazine (50.7 g) and Disponyl AFX4030 (40.6 g). Theisocyanate-terminated prepolymer temperature during dispersion was keptat 50° C. and the dispersion temperature was controlled between 25 to30° C.

Stage 2: Polyurethane vinyl (50/50) hybrid dispersion: To the dispersionprepared in Stage 1 (1000.0 g) was charged BMA (100.0) and STY (27.2 g).After the addition of the additional vinyl monomers the dispersion wasallowed to stir for 1 hour at ambient temperature. To the resultantdispersion was then added a 10% tBHPO solution in water (5.8 g) and a 1%FeEDTA solution in water (2.9 g) followed by feeding a 2.5% IAA solutionin water (17.8 g) over a period of 45 minutes. The resultantpolyurethane vinyl hybrid dispersion was filtered through 75 micronfilter cloths.

EXAMPLE XI

Stage 1: Polyurethane dispersion: A dispersion of theisocyanate-terminated prepolymer was made by feeding 358.0 g of theisocyanate-terminated prepolymer described in Example IX at 50° C. over1 hour to deionised water (942.6 g) containing n-methylmorpholine (24.6g), 15.2% hydrazine (31.3 g) and Disponyl AFX4030 (25.1 g). Theisocyanate-terminated prepolymer temperature during dispersion was keptat 50° C. and the dispersion temperature was controlled between 25 to30° C.

Stage 2: Polyurethane vinyl (50/50) hybrid dispersion: To the dispersionprepared in Stage 1 (1390.2 g) was charged BMA (112.50 g) and STY (31.1g). After the addition of the additional vinyl monomers the dispersionwas allowed to stir for 1 hour at ambient temperature. To the resultantdispersion was then added a 10% tBHPO solution in water (6.5 g) and a 1%FeEDTA solution in water (3.3 g) followed by feeding a 2.5% IAA solutionin water (20.1 g) over a period of 45 minutes. The resultantpolyurethane vinyl hybrid dispersion was filtered through 75 micronfilter cloths.

EXAMPLE XII

Stage 1: Polyurethane dispersion: A 3000 cm³ flask equipped with athermometer and overhead stirrer was charged with CHDM (76.8), DMPA(192.0 g), Terathane 1000 (902.2 g), TDI (749.1 g), Ionol cp (0.3) andMMA (480.0 g). The reaction was allowed to exotherm to 50° C. After theexotherm was complete the reaction was kept at 85° C. for 2 hours. TheNCO-content of the isocyanate-terminated prepolymer was 4.87%(theoretical 5.02%).

A dispersion of the isocyanate-terminated prepolymer was made by feeding550.0 g of the isocyanate-terminated prepolymer at 50° C. over 1 hour todeionised water (1120.8 g) containing DMEA (32.2 g), EDA (16.3 g) andDisponyl AFX4060 (22.0 g). The isocyanate-terminated prepolymertemperature during dispersion was kept at 60° C. and the dispersiontemperature was controlled between 25 to 30° C.

Stage 2: Polyurethane vinyl (80/20) hybrid dispersion: To the dispersionprepared in Stage 1 (1740.0 g) was added a 10% tBHPO solution in water(2.9 g) and a 1% FeEDTA solution in water (1.4 g) followed by feeding a2.5% IAA solution in water (8.8 g) over a period of 45 minutes. Theresultant polyurethane vinyl hybrid dispersion was filtered through 75micron filter cloths.

EXAMPLE XIII

Stage 1: Polyurethane dispersion: A 1000 cm³ flask equipped with athermometer and overhead stirrer was charged with CHDM (19.2), DMPA(48.0), PEC90 (191.4 g), Rubinate 9279 (221.4 g), Ionol cp (0.1) and MMA(120.0 g). The reaction was allowed to exotherm to 50° C. After theexotherm was complete the reaction was kept at 85° C. for 2 hours. TheNCO-content of the isocyanate-terminated prepolymer was 4.45%(theoretical 4.87%).

A dispersion of the isocyanate-terminated prepolymer was made by feeding500.0 g of the isocyanate-terminated prepolymer at 60° C. over 1 hour todeionised water (939.7 g) containing DMEA (29.2 g), 15.2% hydrazine(47.2 g) and Disponyl AFX4030 (40.0 g). The isocyanate-terminatedprepolymer temperature during dispersion was kept at 60° C. and thedispersion temperature was controlled between 25 to 30° C.

Stage 2: Polyurethane vinyl (80/20) hybrid dispersion: To the dispersionprepared in Stage 1 (1560.0 g) was added a 10% tBHPO solution in water(3.5 g) and a 1% FeEDTA solution in water (1.7 g) followed by feeding a2.5% IAA solution in water (10.6 g) over a period of 45 minutes. Theresultant polyurethane vinyl hybrid dispersion was filtered through 75micron filter cloths.

Sediment Determination:

Sediment is unstabilised solid material (in the order of microns ratherthan nanometers) which is formed during dispersing or reaction and whichwill settle or precipitate upon storage and/or heating. It may bedetermined quantitatively by centrifuging. The sediment content wasdetermined by taking 50 cm³ of the resultant dispersion of the examplesprepared above, diluting this with water (1:1) and centrifuging thediluted composition for 15 minutes at 1500 rpm (276G) rpm in acentrifuge tube.

Each division on the tube tip represents 0.05 cm³ or 0.05% sediment. Theoutcome, i.e. the level of solid sediment in the tube tip was thenmultiplied by 2 to take into account the dilution factor. TABLE 1Example I II III IV V VI VII Solids (%) 30.5 33.2 33.0 33.8 33.6 33.730.4 pH 7.9 8.4 7.9 8.3 8.8 8.8 8.1 Viscosity (mPa · s) * 140 260 230380 380 288 180 Sediment (%) # 0.2 0.2 <0.05 <0.05 0.3 0.1 0.3Absorbance ** 25 16 69 50 17 33 113 Particle size (nm) 80.2 87.8 94.6119.4 98.6 172.8 170.2 MFFT (° C.) 18 18 16 <5 10 9 <5 KH (s) *** 181200 169 176 160 132 160 Elongation at break (%) 147 127 62 107 104 118148 Yellowness ## 1.6/2.9 0.5/2.6 0.4/1.6 0.2/2.6 0.3/2.8 0.4/2.60.2/2.9 Yellowing (Δb) 1.3 2.1 1.2 2.4 2.5 2.2 2.7 Example VIII IX X XIXII XIII Solids (%) 33.6 33.4 33.6 33.1 34.0 33.3 pH 8.2 8.1 7.9 7.7 8.18.1 Viscosity (mPa · s) * 48 376 432 210 136 516 Sediment (%) # 0.4 0.2<0.05 0.2 0.4 <0.05 Absorbance ** 107 7 4 127 18 3 Particle size (nm)115.1 70 77 179 67.6 57.1 MFFT (° C.) 12 20 45 40 <5 17 KH (s) *** 146175 162 169 154 179 Elongation at break (%) 55 59 65 59 115 150Yellowness ## 0.3/2.1 0.1/1.8 0.4/2.4 1.3/3.0 0.3/2.6 0.3/2.6 Yellowing(Δb) 1.8 1.7 2.0 1.7 2.3 2.3* A Brookfield viscosity at 25° C.** The measured absorbance by spectrometry at 650 nm using a path lengthof 1 mm.*** The König Hardness (KH) of a dried film cast on a glass plate with awet film thickness of 80 micron.# The sediment was determined before filtration.## The yellowness of the dried film before UV exposure/after UV exposurewhere the UV exposure was 10 × 400 mJ/cm².

COMPARATIVE EXAMPLE I Preparation of a Polyurethane Vinyl HybridDispersion with an Acid Value of 23 mg KOH/g

A 1000 cm³ flask equipped with a thermometer and overhead stirrer wascharged with DMPA (28.6 g), CHDM (15.6 g), Terathane 1000 (273.6 g), MMA(130.0 g), Rubinate 9279 (202.2 g) and Ionol cp (0.1 g). The reactionwas allowed to exotherm to 70° C. After the exotherm was complete thereaction was kept at 85° C. for 2 hours. The NCO-content of theisocyanate-terminated prepolymer was 4.26% (theoretical 4.62%).

A dispersion of the isocyanate-terminated prepolymer was made by feeding500.0 g of the isocyanate-terminated prepolymer at 60° C. over 1 hour to1127.8 g of deionised water containing DMEA (20.1 g), 15.2% hydrazine(48.1 g) and ABEX2545 (24.0 g). The isocyanate-terminated prepolymertemperature during dispersion was kept at 50° C. and the dispersiontemperature was controlled between 25 to 30° C.

Due to large sediment value of the polyurethane dispersion (>20% beforefiltration) the process to prepare polyurethane vinyl hybrid wasdiscontinued.

COMPARATIVE EXAMPLE II

This example was prepared as described in Example 12, U.S. Pat. No.5,137,961 and comprises the preparation of a polyurethane prepolymerbased on toluene diisocyanate (246.0 g, 80/20 ratio for the 2,4- and2,6-isomers), diphenylmethane diisocyanate (246.0 g, 75/25 ratio for the4,4′ and 2,4′ isomers), terathane-1000 polyetherdiol (579.2 g, OH=114.3mg KOH/g), CHDM (8.8 g), DMPA (120.0 g), BA (133.3 g), MMA (266.7 g),STY (400.0 g) and Topanol O inhibitor (1.6 g).

The polyurethane dispersion was prepared by the addition of 400.0 gprepolymer to an aqueous phase which contained triethyl amine (26.1 g),hydrazine (1.0) and water (841.2 g). The residual hydrazine (0.5 g) wassimultaneously fed, also in 1 hour at ambient temperature. The degree ofneutralisation on equivalents was 1.44:1 and the total degree ofextension was 0.24:1.

The final polyurethane vinyl (50/50) hybrid polymer was prepared byradical polymerisation of the vinyl monomers in the dispersion as wellas additional vinyl monomers according to the following recipe:Polyurethane dispersion (851.8 g), deionised water (309.6 g), tBHPO (1.3g), IAA, 1% solution in water (60.0 g), STY (88.6 g), MMA (15.6 g),acrylonitrile (18.0 g) and BA (11.1 g).

However was not possible to prepare the U/A from the dispersionsdescribed above following the procedure described in example 12, U.S.Pat. No. 5,137,961. The exact reproduction coagulated immediately afterthe start of the redox reaction resulting in about 100% sediment. Theresultant specification did not correspond to the specifications givenin U.S. Pat. No. 5,137,961.

1. An aqueous composition with a sediment content <5%, comprising apolyurethane dispersion and containing ≦5 wt % of1-methyl-2-pyrrolidinone by weight of the polyurethane, wherein thepolyurethane has an acid value in the range of from 25 to 65 mgKOH/g andis obtained by the reaction of: A) an isocyanate-terminated prepolymerformed from components comprising: (i) 36 to 60 wt % of at least onearomatic polyisocyanate; (ii) 0 to 30 wt % of at least one aliphaticpolyisocyanate; (iii) 0 to 15 wt % of at least one isocyanate-reactivepolyol bearing ionic and/or potentially ionic water-dispersing groupswith a weight average molecular weight ≦500 g/mol; (iv) 0 to 10 wt % ofat least one isocyanate-reactive polyol bearing non-ionicwater-dispersing groups; (v) 0 to 15 wt % of at least oneisocyanate-reactive polyol with a weight average molecular weight ≦500g/mol not comprised by (iii) or (iv); (vi) 20 to 58 wt % of at least oneisocyanate-reactive polyol not comprised by (iii), (iv) or (v); where(i)+(ii)+(iii)+(iv)+(v)+(vi) add up to 100 wt %; where the NCO/OH ratiois in the range of from 1.2:1 to 2.5:1; and B) at least oneactive-hydrogen chain extending compound; where the active-hydrogen/NCOratio is in the range of from 0.4:1 to 1.3:1; in the presence of (a) ≦5wt % of 1-methyl-2-pyrrolidinone by weight polyurethane; and (b) atleast one reactive diluent.
 2. An aqueous composition with a sedimentcontent ≦5% comprising a polyurethane vinyl hybrid dispersion andcontaining ≦0.5 wt % of 1-methyl-2-pyrrolidinone by weight of thecomposition; wherein the polyurethane has an acid value in the range offrom 25 to 65 mgKOH/g and is obtained by the reaction of: A) anisocyanate-terminated prepolymer formed from components comprising: (i)36 to 60 wt % of at least one aromatic organic polyisocyanate; (ii) 0 to30 wt % of at least one aliphatic organic polyisocyanate; (iii) 0 to 15wt % of at least one isocyanate-reactive polyol bearing ionic and/orpotentially ionic water-dispersing groups with a weight averagemolecular weight ≦500 g/mol; (iv) 0 to 10 wt % of at least oneisocyanate-reactive polyol bearing non-ionic water-dispersing groups;(v) 0 to 15 wt % of at least one isocyanate-reactive polyol with aweight average molecular weight ≦500 g/mol not comprised by (iii) or(iv); (vi) 20 to 58 wt % of at least one isocyanate-reactive polyol notcomprised by (iii), (iv) or (v); where (i)+(N)+(iii)+(iv)+(v)+(vi) addup to 100 wt %; where the NCO/OH ratio is in the range of from 1.2:1 to2.5:1; and B) at least one active-hydrogen chain extending compound;where the active-hydrogen/NCO ratio is in the range of from 0.4:1 to1.3:1; in the presence of (a) ≦5 wt % of 1-methyl-2-pyrrolidinone byweight of polyurethane and (b) at least one reactive diluent.
 3. Anaqueous composition according to claim 2 wherein the ratio ofpolyurethane to vinyl polymer in the polyurethane vinyl hybrid is in therange of from 95:5 to 30:70.
 4. An aqueous composition according toclaim 2 wherein the calculated Tg of the vinyl polymer in thepolyurethane vinyl hybrid is in the range of from 20 to 120° C.
 5. Anaqueous composition according to claim 1 wherein at least 20 to 80 wt %of component (i) consists of methylenebis(phenyl isocyanate) (MDI). 6.An aqueous composition according to claim 1 where components(i)+(ii)+(iii)+(v) add up to ≧42 wt %.
 7. An aqueous composition toclaim 1 wherein the reactive diluent comprises between 5 and 40% byweight of both the isocyanate-terminated prepolymer and the reactivediluent together.
 8. An aqueous composition according to claim 1 whereinthe reactive diluent comprises vinyl monomers.
 9. An aqueous compositionaccording to claim 8 wherein the reactive diluent comprises 40 to 100 wt% of vinyl monomer selected from the group consisting of methylmethacrylate and ethylmethacrylate.
 10. An aqueous composition accordingto claim 8 wherein the reactive diluent comprises <45 wt % of styreneand styrene based vinyl monomers.
 11. An aqueous composition accordingto claim 1 wherein the ionic water-dispersing groups in theisocyanate-terminated prepolymer are neutralised with a neutralisingagent in the range of from 0.5:1 to 1.4:1.
 12. An aqueous compositionaccording to claim 1 wherein the ionic- water-dispersing groups areanionic water-dispersing groups and ≧60 wt % of the anionicwater-dispersing groups in the isocyanate-terminated prepolymer areneutralised with an oxygen containing amine.
 13. An aqueous compositionaccording to claim 12 where the oxygen containing amine is selected fromthe group consisting of N-ethyl morpholine; N-methyl morpholine; andR¹(R²)NR³OH with a Mn in the range of from 88 to 118, where R₁, R₂ andR₃ are independently C₁ to C₄ alky.
 14. An aqueous composition accordingto claim 1 which when in the form of film has a König Hardness ≧120s.15. An aqueous composition according to claim 1 which when in the formof a film has an elongation at break ≧50% and a König Hardness ≧120s.16. An aqueous composition according to claim 1 with a minimum filmforming temperature ≦500C.
 17. An aqueous composition according to claim1, containing ≦2 wt % of a co-solvent by weight of the composition witha minimum film forming temperature ≦23° C. and which when in the form ofa film has a König Hardness ≧120s.
 18. An aqueous composition accordingto claim 1 with a solids content in the range of from 20 to 55 wt %. 19.An aqueous composition according to claim 1 with a weight averageparticle size less than 500 nm.
 20. A process for making an aqueouscomposition with a sediment content ≦5%, comprising a polyurethanedispersion and containing ≦5 wt % of 1-methyl-2-pyrrolidinone by weightof the polyurethane, wherein the polyurethane has an acid value in therange of from 25 to 65 mgKOH/g, and where the process is carried out insteps comprising: I: reacting in the presence of (a) ≦5 wt % of1-methyl-2-pyrrolidinone by weight of polyurethane and (b) at least onereactive diluent; (i) 36 to 60 wt % of at least one aromaticpolyisocyanate; (ii) 0 to 30 wt % of at least one aliphaticpolyisocyanate; (iii) 0 to 15 wt % of at least one isocyanate-reactivepolyol bearing ionic and/or potentially ionic water-dispersing groupswith a weight average molecular weight ≦500 g/mol; (iv) 0 to 10 wt % ofat least one isocyanate-reactive polyol bearing non-ionicwater-dispersing groups; (v) 0 to 15 wt % of at least oneisocyanate-reactive polyol with a weight average molecular weight ≦500g/mol not comprised by (iii) or (iv); (vi) 20 to 58 wt % of at least oneisocyanate-reactive polyol not comprised by (iii), (iv) or (v); where(i)+(ii)+(iii)+(iv)+(v)+(vi) add up to 100 wt %; where the NCO/OH ratiois in the range of from 1.2:1 to 2.5:1 to form an isocyanate-terminatedprepolymer; II: neutralising the isocyanate-terminated prepolymer with aneutralising agent; III: forming an aqueous dispersion of theisocyanate-terminated prepolymer in water; IV: reacting theisocyanate-terminated prepolymer with at least one active hydrogenchain-extending compound to form the polyurethane; where the activehydrogen/NCO ratio is in the range of from 0.4:1 to 1.3:1; VI:polymerising the reactive diluent.
 21. A process for making an aqueouscomposition with a sediment content ≦5% comprising a polyurethane vinylhybrid dispersion and containing ≦0.5 wt % of 1-methyl-2-pyrrolidinoneby weight of the composition, wherein the polyurethane has an acid valuein the range of from 25 to 65 mgKOH/g, and where the process is carriedout in steps comprising: I: reacting in the presence of (a) ≦5 wt % of1-methyl-2-pyrrolidinone by weight of polyurethane and (b) at least onereactive diluent; (i) 36 to 60 wt % of at least one aromaticpolyisocyanate; (ii) 0 to 30 wt % of at least one aliphaticpolyisocyanate; (iii) 0 to 15 wt % of at least one isocyanate-reactivepolyol bearing ionic and/or potentially ionic water-dispersing groupswith a weight average molecular weight ≦500 g/mol; (iv) 0 to 10 wt % ofat least one isocyanate-reactive polyol bearing non-ionicwater-dispersing groups; (v) 0 to 15 wt % of at least oneisocyanate-reactive polyol with a weight average molecular weight ≦500g/mol not comprised by (iii) or (iv); (vi) 20 to 58 wt % of at least oneisocyanate-reactive polyol not comprised by (iii), (iv) or (v); where(i)+(ii)+(iii)+(iv)+(v)+(vi) add up to 100 wt %; where the NCO/OH ratiois in the range of from 1.2:1 to 2.5:1 to form an isocyanate-terminatedprepolymer; II: neutralising the isocyanate-terminated prepolymer with aneutralising agent; III: forming an aqueous dispersion of theisocyanate-terminated prepolymer in water; IV: reacting theisocyanate-terminated prepolymer with at least one active hydrogenchain-extending compound to form the polyurethane; where the activehydrogen/NCO ratio is in the range of from 0.4:1 to 1:3:1; V: optionallyadding additional vinyl monomer; VI: polymerising the reactive diluentand vinyl monomer added in step V.
 22. A process according to claim 20where step II is carried out by means of at least an in-line mixer. 23.A process according to claim 20 where the time between step III and stepIV is less than 40 minutes.
 24. A process according to claim 20 where atleast 50 wt % of the active- hydrogen chain extending compound ispresent in the water before completion of step III.
 25. A method ofcoating a substrate using an aqueous composition according to claim 1comprising applying the composition to a substrate.
 26. A substratehaving a coating obtained from an aqueous composition according toclaim
 1. 27. A substrate according to claim 26 selected from the groupconsisting of wood, metal, concrete, plastic and glass.
 28. A floorhaving a coating obtained from an aqueous composition according to claim1.